This invention relates to electric machines, and more specifically to an induction disk motor using a ferromagnetic metal tape for making one or both of the stator body and rotor body of the machine. The metal tape may be amorphous metal or thin silicon or carbon steel.
Induction disk motors are well known and are commonly used in industrial applications. D-C disk motors have been developed for industrial and electric vehicle drives but have numerous known limitations. Induction disk motors with solid rotors are limited in efficiency due to their large effective air gap unconstrained current path and iron core losses.
A squirrel cage induction motor would be very useful for applications such as the wheel motor of an electric car in view of the motor ruggedness, reliability and efficiency; however, these motors are difficult to apply to the disk form which would be preferable in such applications.
Amorphous metal tape having excellent magnetic properties have recently become available at about one-fourth the cost of conventional transformer steel used in electric machines. These tapes exhibit a core loss about one-fourth that of the conventional silicon iron and have very high permeability. Amorphous metal tapes, however, are not available in the usual lamination form now needed for the construction of conventional electric machines so that the desirable magnetic properties and low cost of the amorphous metal glass has not been used for an electric machine. The tape is made very thin (of from 0.0005 to 0.003 inch thick) and in widths of up to about two inches and has high resistivity resulting in superior high frequency properties. Good efficiency is then attainable even at high speeds.
Amorphous metal tapes having magnetic properties desired for application to electric machines are disclosed in U.S. Pat. Nos. 3,856,513, dated Dec. 24, 1974, in the name of Chen et al.; 3,881,542, dated May 6, 1975, in the name of Polk et al.; 4,052,201, dated Oct. 4, 1977, in the name of Polk et al.; 4,059,441, dated Nov. 22, 1977, in the name of Ray et al. and 4,067,732, dated Jan. 10, 1978, in the name of Ray. A survey of metal glass technology is given in the article "Metallic Glasses" by John J. Gilman appearing in Physics Today, May 1975, pages 46 to 53. Some attempts are being made to exploit the advantages of the properties of these metal tapes, for example, for acoustic devices as shown in U.S. Pat. No. 3,838,365.
As an alternative to amorphous metal tape, thin strip comprised of silicon steel, such as Armco M22, or as another alternative, "common iron" may be employed.
An object of the present invention is to provide an electric machine construction which capitalizes on the tape form of amorphous metal, silicon steel, or carbon steel, and changes the shape and electromagnetic configuration of the electric machine so that it can utilize the tape.